Todd Kohlhepp, a registered sex offender who has been arrested in connection with the kidnapping of Kala Brown and Charles David Carver is shown in this booking photo provided in Spartanburg, South Carolina, November 3, 2016. Photo courtesy of Spartanbur

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(Reuters) - A South Carolina man suspected of chaining a woman inside a storage shed on his rural property was charged with four murders and denied bail on Sunday based on his confession to a massacre at a motorcycle shop 13 years ago, South Carolina media reported.

The suspect, Todd Kohlhepp, may be linked to as many as seven deaths, Spartanburg County Sheriff Chuck Wright said on Saturday. Investigators have searched his property for more bodies after that of the kidnapped woman's boyfriend was found there in a shallow grave.

After being freed on Thursday, the woman told authorities she had witnessed Kohlhepp shoot her boyfriend. The couple had been missing for two months.

Kohlhepp was denied bail on the quadruple homicide, the Spartanburg Herald-Journal reported from the courtroom at the county jail, which was filled with relatives of the victims and reporters, the newspaper said on its website. A photograph showed Kohlhepp, 45, appearing before the judge in an orange jumpsuit.

Kohlhepp, a registered sex offender who works as a realtor, declined two opportunities to speak in front of the victims' families, the Herald-Journal reported.

"Not at this time, sir," Kohlhepp told the judge, his hands folded behind his back.

Northwestern South Carolina was already shocked by the kidnapping case that came to light on Thursday when the sheriff on Saturday revealed Kohlhepp's confession to the quadruple homicide, one of the county's oldest unsolved cases as well as one of its most sensational.

The so-called Superbike case is named after the motorsports shop in Spartanburg County where four people were executed in 2003. Wright said he believed the confession based on details that Kohlhepp provided.

"I am 100 percent convinced that what this man told us was factual," Wright said, according to the Herald-Journal. "He told us some stuff that nobody else should know. I don't mind telling you, this is a pretty big deal."

Police found 30-year-old Kala Brown chained inside a locked container on Kohlhepp's property on Thursday. A day later, Kohlhepp was charged with keeping her there for two months.

Also on Friday, officials identified a body found in a shallow grave on that property as Kala Brown's boyfriend, Charles Carver, 32, who had been shot multiple times, the Herald-Journal reported, citing the county coroner.

More bodies may be buried on the 96-acre (39-hectare) property, Wright said, based on Brown's account given to investigators after she was freed.